William J. Hodgetts. 
43 
VEGETATIVE PRODUCTION OF FLATTENED 
PROTON EM A IN TETRAPHIS PELLUCID A. 
By William J. Hodgetts. 
[With One Figure in the Text.] 
1.—Introduction. 
N the great majority of mosses the protonema, or early phase of 
l the gametophyte, is filamentous and monosiphonous, con¬ 
sisting of a single branching row of cells from some of which there 
arise buds which develop into leafy moss-plants—and this whether 
it proceeds from the germinating spore and thus forms part of 
the normal life-cycle of the moss-plant, or whether it arises 
by outgrowth of certain cells of the moss-plant or of the 
sporogonium itself (in the last case forming an example of apospory) 
and thus forms a deviation which lengthens or (by apospory) 
shortens the life-cycle, serving for vegetative propagation. 
There are certain exceptions to this rule, in which the whole or 
part of the protonema is ribbon-like or cylindrical. The remarkable 
protonema of Schistostega, which sends up from its creeping filamen¬ 
tous portion erect filaments whence arise repeatedly branched chains 
of lens-like cells all lying in the same horizontal plane, is strictly 
monosiphonous although the branching chains of cells in the aerial 
assimilating portion form virtually a plate. True thalloid or flattened 
protonemata occur in the monogeneric orders Sphagnales ( Sphag¬ 
num) and Andreasales ( Andrecea ), the Tetraphidales (with the two 
genera Tetraphis and Tetradontium), the Buxbaumiales (with the two 
genera Buxbaumia and Diphyschun ), and the rare and isolated genus 
CEdipodium which is usually placed in or near the family Splach- 
nacese though its affinities are obscure. It will be noted that with 
the exception of CEdipodium, flattened protonemata are character¬ 
istic of four out of the five orders of mosses which are for other 
reasons regarded as being relatively primitive. 1 
In Sphagmim the germ-tube arising from the spore soon 
becomes a plate of cells which may reach a considerable size before 
producing, usually from a marginal cell near the base, the bud from 
which a new moss-plant develops. Muller 2 has made the interesting 
observation that numerous secondary protonemata, or innovation 
lobes, arise as outgrowths at various points from marginal cells of 
1 See classification given by Cavers, “ Inter-relationships of the Bryo- 
phyta,” New Phytologist, Vol. 10, 1911, pp. 26-34. 
s Muller, in Engler and Prantl, Teil 1, Abt. 3, p. 163, Fig. 82. 
